Interferometer is a widely used instrument. The constituents of interferometers may vary, but they all comprise these essential elements: a source, a splitter, two paths, and a detection apparatus. The source may generate acoustical, electromagnetic, and light wave, which is split into two paths by the splitter. The detection apparatus compares waves from the two paths, and determine their variational differences. Interferometer is a powerful instrument, which is capable of probing micro, meso, and macro systems. A system under test may be the source, the splitter, or an external system inserted into an interferometer path. We can infer the physical characteristics of the system under test from the observed variational differences.
An interferometer with a continuous wave source requires both the interferometer and system under test to be stable and stationary. Any random and vibrational motion will blur the variational differences, and mask the physical characteristics of the system under test. An interferometer with a short-pulsed source will freeze a transient natural event. However, with a conventional interferometer we are not able to decipher completely the variational difference created by a single transient event. Multiple pulses and events are needed, thus the short pulse and the transient event have to be exactly and repeatedly reproduced. This may not be possible with all transient events.
Digitizing receiver is another widely used instrument. It comprises a radio frequency (RF) receiver and a digitizer. In a receiving process, the RF receiver first converts an RF signal to an intermediate frequency (IF) signal, and then to a video signal. A digitizer converts the analog video signal to a digital signal. The capability of a digitizer depends on its sampling rate. Digitizers with sampling rate of 200 MHz are commercially available. Digitizers with sampling rate of 1 GHz have been reported. Depending on the capability of a digitizer, the down conversion to a video signal may not be needed and a digitizer may directly digitize a IF signal. A down conversion will filter away many intrinsic traits of a transient event. Most radar receivers have IF frequency of 60 MHz. More sophisticated RF receivers have IF frequency of 10 GHz to preserve the intrinsic traits of subnanosecond RF pulses. It is still impossible for a digitizing receiver to completely capture the intrinsic traits of a single RF pulse with frequency of 10 GHz and pulse width of 1 GHz. Multiple pulses and events are again needed.
In light of the above, there is a need in the art for new apparatus which are capable of capturing the intrinsic traits of and determining the variational differences created by a random, chaotic, turbulent, or transient phenomenon. Furthermore it will reveal the physical traits of a single transient event without instability blurring. An interferoceiver with RF signal train generator will fulfill the needs to capture transient traits and to overcome the blurring. The physical principle for the new interferoceiver to capture an transient event is the same as that for optical fiber based radars with an RF signal train generator.